Featuring a memorable line still remembered by film enthusiasts, the 1951 film The Day the Earth Stood Still helped usher in a new era in science fiction. A "flying saucer" movie with a message, it was widely imitated, but never duplicated, throughout the decade.

Poster for the 1951 sci-fi classic The Day the Earth Stood Still. The Kobal Collection/20th Century Fox. Reproduced by permission.

When The Day the Earth Stood Still opened in theaters in September 1951, the United States and the Soviet Union were locked in a nuclear arms race. Each side distrusted the other. Each was in the process of developing enough atomic firepower to destroy the entire planet. The film, like many great science-fiction stories, addressed these important issues in fantasy form. The plot concerns a flying saucer that lands in Washington, D.C., containing the alien...